// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
package qunar.tc.decompiler.modules.renamer;

import qunar.tc.decompiler.code.CodeConstants;
import qunar.tc.decompiler.main.extern.IIdentifierRenamer;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;

public class ConverterHelper implements IIdentifierRenamer {
    private static final Set<String> KEYWORDS = new HashSet<>(Arrays.asList(
            "abstract", "do", "if", "package", "synchronized", "boolean", "double", "implements", "private", "this", "break", "else", "import",
            "protected", "throw", "byte", "extends", "instanceof", "public", "throws", "case", "false", "int", "return", "transient", "catch",
            "final", "interface", "short", "true", "char", "finally", "long", "static", "try", "class", "float", "native", "strictfp", "void",
            "const", "for", "new", "super", "volatile", "continue", "goto", "null", "switch", "while", "default", "assert", "enum"));
    private static final Set<String> RESERVED_WINDOWS_NAMESPACE = new HashSet<>(Arrays.asList(
            "con", "prn", "aux", "nul",
            "com1", "com2", "com3", "com4", "com5", "com6", "com7", "com8", "com9",
            "lpt1", "lpt2", "lpt3", "lpt4", "lpt5", "lpt6", "lpt7", "lpt8", "lpt9"));

    private int classCounter = 0;
    private int fieldCounter = 0;
    private int methodCounter = 0;
    private final Set<String> setNonStandardClassNames = new HashSet<>();

    @Override
    public boolean toBeRenamed(Type elementType, String className, String element, String descriptor) {
        String value = elementType == Type.ELEMENT_CLASS ? className : element;
        return value == null ||
                value.length() <= 2 ||
                !isValidIdentifier(elementType == Type.ELEMENT_METHOD, value) ||
                KEYWORDS.contains(value) ||
                elementType == Type.ELEMENT_CLASS && (
                        RESERVED_WINDOWS_NAMESPACE.contains(value.toLowerCase(Locale.ENGLISH)) ||
                                value.length() > 255 - ".class".length());
    }

    /**
     * Return {@code true} if, and only if identifier passed is compliant to JLS9 section 3.8 AND DOES NOT CONTAINS so-called "ignorable" characters.
     * Ignorable characters are removed by javac silently during compilation and thus may appear only in specially crafted obfuscated classes.
     * For more information about "ignorable" characters see <a href="https://bugs.openjdk.java.net/browse/JDK-7144981">JDK-7144981</a>.
     *
     * @param identifier Identifier to be checked
     * @return {@code true} in case {@code identifier} passed can be used as an identifier; {@code false} otherwise.
     */
    private static boolean isValidIdentifier(boolean isMethod, String identifier) {

        assert identifier != null : "Null identifier passed to the isValidIdentifier() method.";
        assert !identifier.isEmpty() : "Empty identifier passed to the isValidIdentifier() method.";

        if (isMethod && (identifier.equals(CodeConstants.INIT_NAME) || identifier.equals(CodeConstants.CLINIT_NAME))) {
            return true;
        }

        if (!Character.isJavaIdentifierStart(identifier.charAt(0))) {
            return false;
        }

        char[] chars = identifier.toCharArray();

        for (int i = 1; i < chars.length; i++) {
            char ch = chars[i];

            if ((!Character.isJavaIdentifierPart(ch)) || Character.isIdentifierIgnorable(ch)) {
                return false;
            }
        }

        return true;

    }

    // TODO: consider possible conflicts with not renamed classes, fields and methods!
    // We should get all relevant information here.
    @Override
    public String getNextClassName(String fullName, String shortName) {
        if (shortName == null) {
            return "class_" + (classCounter++);
        }

        int index = 0;
        while (index < shortName.length() && Character.isDigit(shortName.charAt(index))) {
            index++;
        }

        if (index == 0 || index == shortName.length()) {
            return "class_" + (classCounter++);
        } else {
            String name = shortName.substring(index);
            if (setNonStandardClassNames.contains(name)) {
                return "Inner" + name + "_" + (classCounter++);
            } else {
                setNonStandardClassNames.add(name);
                return "Inner" + name;
            }
        }
    }

    @Override
    public String getNextFieldName(String className, String field, String descriptor) {
        return "field_" + (fieldCounter++);
    }

    @Override
    public String getNextMethodName(String className, String method, String descriptor) {
        return "method_" + (methodCounter++);
    }

    // *****************************************************************************
    // static methods
    // *****************************************************************************

    public static String getSimpleClassName(String fullName) {
        return fullName.substring(fullName.lastIndexOf('/') + 1);
    }

    public static String replaceSimpleClassName(String fullName, String newName) {
        return fullName.substring(0, fullName.lastIndexOf('/') + 1) + newName;
    }
}